より高速・長寿命バッテリー技術で飛躍的進展（UH researchers advance longer-lasting, faster-charging batteries）

2025-10-01 ヒューストン大学

ヒューストン大学の研究チームは、次世代リチウム電池開発に向け、単価金属（リチウム、ナトリウム、カリウム）と多価金属（マグネシウム、カルシウム、アルミニウム）を比較検討したレビューを発表した。従来のグラファイト負極は容量に限界があるが、リチウム金属は約10倍の容量を持つ。しかしデンドライト形成による短絡リスクが課題である。一方、多価金属は資源的に豊富で安全性も高く、より大きなエネルギー貯蔵能力を有する可能性があるが、イオン移動速度の遅さが難点とされる。研究者らは電極表面のテクスチャ制御や新規電解質設計によって課題克服を目指し、持続可能で高速充電可能な次世代電池技術への道筋を示した。

＜関連情報＞

一価金属と多価金属の電池陽極の違い The contrast between monovalent and multivalent metal battery anodes

Yuanjian Li, Sonal Kumar, Gaoliang Yang, Jun Lu, […] , and Zhi Wei Seh
Science Published:18 Sep 2025
DOI:https://doi.org/10.1126/science.adl5482

Editor’s summary

Graphite is regularly used as the anode for lithium ion batteries, but it has its limitations and researchers have thus considered a number of metal alternatives. These include monovalent species such as lithium, sodium, and potassium and multivalent ones such as calcium, magnesium, and aluminum, which also have the advantage of being earth abundant. In a Review, Li et al. contrasted the electrochemical behavior of both types of metals when coupled with nonaqueous electrolytes. A key goal was to highlight where knowledge from one group has relevance to the other and where specific problems may arise with only one group or one specific metal, with the aim of guiding the development of next-generation batteries. —Marc S. Lavine

Structured Abstract

BACKGROUND

Batteries are an integral component of an electrified modern society, as they power consumer electronics and electric vehicles and help to integrate intermittent renewable energy into smart grids. With performance requirements constantly increasing, there is much demand for high–energy density and low-cost batteries, beyond the capabilities of widely commercialized lithium (Li)–ion batteries. For a battery anode, Li metal is considered to be one of the most attractive choices because of its high theoretical specific capacity and negative electrochemical potential. Other promising anode candidates include sodium (Na), potassium (K), magnesium (Mg), calcium (Ca), and aluminum (Al) metals, as their crustal abundance is higher than that of Li. Furthermore, all these monovalent (Li, Na, K) and multivalent (Mg, Ca, Al) metal anodes are indispensable for next-generation high-energy, low-cost metal-sulfur and metal-air batteries.

ADVANCES

After decades of research and development, the practical applications of the monovalent and multivalent metal anodes in nonaqueous rechargeable batteries are still plagued by common problems and specific challenges. (i) Irregular deposition is a common occurrence during electrochemical plating of Li, Na, K, Mg, Ca, and Al metals; however, the deposition morphologies are distinct for different metals. Specifically, monovalent metals easily grow into whisker-like, moss-like, and tree-like dendrites, whereas multivalent metals prefer deposition morphologies such as interconnected platelets and random fibers or spheres. There are also some reports of spherical dendrite growth for monovalent anodes and tree-like growth for multivalent anodes. (ii) Owing to their negative electrochemical potential, the considered metal anodes can readily react with electrolyte components such as solvents and salts to produce a heterogeneous interface layer, comprising both organics and inorganics. In monovalent batteries, Li⁺, Na⁺, and K⁺ cations are mostly surrounded by solvent molecules, and the as-formed solvent-dominated solvation structure leads to the production of organic-rich solid-electrolyte interphases (SEIs) on Li, Na, and K anodes, which permit the facile conduction of their respective ions. Conversely, the multivalent nature of Mg²⁺, Ca²⁺, and Al³⁺ cations not only induces a strong tendency to form anion-participated solvation structure in conventional nonaqueous electrolytes but also tends to form inorganic-rich SEI layers. This makes it more difficult for multivalent cations with high charge density to diffuse across the nanointerface between the electrolyte and their corresponding metal anodes.

OUTLOOK

With a comprehensive understanding of the commonalities and differences between the electrochemical characteristics of monovalent and multivalent metal anodes, some general design principles and universal trends for these metal anodes emerge. (i) The desired deposition morphology for reversible metal cycling should comprise homogeneous and closely packed crystals with a specific crystallographic orientation, for example, (110) for Li, Na, and K; (002) for Mg; and (111) for Ca and Al. (ii) A favorable SEI usually requires similar homogeneous structures (e.g., multilayer and monolithic structures) yet different chemical compositions (e.g., a fluorinated inorganic-rich SEI for Li, Na, and K versus a hydrogenated organic-rich SEI for Mg and Ca) to achieve some universal merits of high ion conductivity, electronic insulation, (electro)chemical stability, and mechanically rigid-flexible synergy. (iii) Smart electrolyte design strategies are required to achieve desired deposition morphology and SEI chemistries, for example, (locally) high salt concentration and weakly solvating electrolytes for monovalent systems versus strongly solvating and weakly ion-paring electrolytes for multivalent systems. The successful commercialization of these metal anode-based battery technologies further demands leveraging intrinsic advantages for specific applications, for example, high-energy Li-metal batteries for long-range electric vehicles, cost-effective Na- and K-metal batteries for large-scale energy storage, and thermally resilient Mg-, Ca-, and Al-metal batteries for extreme-environment applications.

Electrochemical behavior of monovalent and multivalent metal anodes.
In the monovalent battery (left), cations tend to coordinate with solvent molecules, forming a solvent-dominated electrolyte solvation structure that is easily reduced to form an organic-rich, ion-conducting interphase. In the multivalent battery (right), the stronger Coulombic force of multivalent cations toward anions leads to an anion-participated electrolyte solvation structure, the decomposition of which induces the formation of inorganic-rich, ion-insulating interphases. Furthermore, unlike monovalent metals, which easily grow into whisker-like, moss-like, and tree-like dendrites, multivalent metals prefer deposition morphologies such as interconnected platelets and random fibers or spheres.

Abstract

Monovalent (lithium, sodium, potassium) and multivalent (magnesium, calcium, aluminum) metal anodes are promising alternatives to graphite anodes for overcoming the performance limitations of lithium-ion batteries. In this Review, we compare and contrast their electrochemical behaviors in nonaqueous electrolytes by discussing their common challenges of irregular metal deposition and unstable solid electrolyte interphases (SEIs), as well as their differences, which are due to dissimilar surface energies and cation charge densities. General design strategies for electrode, electrolyte, and interphase are proposed to enable horizontally deposited metals with preferred crystallographic orientations and stable SEIs with distinct chemical compositions yet similar structural homogeneity. Finally, we assess the specific advantages and unresolved challenges of each system, providing cross-disciplinary insights to advance high-energy and low-cost metal-anode batteries for next-generation energy storage.